Wide dynamic range (WDR) image generators in the related art may be categorized into TRC types and TMO (Tone Mapping Operation) types. A TRC type calculates a proper tone curve of images, and performs tone-mapping based on the proper tone curve. A TMO type performs tone-mapping by using an operator calculating a luminance component proper to each pixel based on pre-calculated statistics of images.
The TRC type has a fast calculation time and a fast task completion time, with deteriorating performance. In contrast, the TMO type has better performance, but with a relatively long calculation time and a relatively slow task completion time.
A structure of a WDR image generator embodying such the TMO type tone mapping is shown in FIG. 1. FIG. 1 is a block diagram illustrating a related WDR image generator. A color space transfer to RGB block 1 shown in FIG. 1 transfers RGB (Red, Green and Blue) information of an input image into YCbCr color space having a brightness component (Y) and a chrominance component (C). Here, a mathematical formula of the luminance gain component (Y) is as follows:Lw=0.2654*RW+0.6704*GW+0.0642*Bw  FORMULA 1
A scene luminance calculation block 2 outputs only the luminance component Lw(i, j and tk)) in the YCbCr color space transferred from the color space transfer to RGB 1. A log-average luminance calculation block 5 calculates the luminance sum of the image by using an output cumulative value of the scene luminance calculation 2 and a natural log. This calculation is as follows:
                              L          avg                =                  exp          (                                    ∑                              log                ⁡                                  (                                      δ                    +                                          L                      w                                                        )                                                      N                    )                                    FORMULA        ⁢                                  ⁢        2            
The log-average luminance calculation 5 calculates an average value (Lavg(tk−1)) of the luminance components of the images by using above Formula 1 and Formula 2 and it induces Ls of a next image by using a linear scaling parameter ‘α’ as follows:
                                          L            s                    ⁡                      (                          ⅈ              ,              j              ,                              t                k                                      )                          =                              α                                          L                avg                            ⁡                              (                                  t                                      k                    -                    1                                                  )                                              *                                    L              w                        ⁡                          (                              ⅈ                ,                j                ,                                  t                  k                                            )                                                          FORMULA        ⁢                                  ⁢        3            
Ld that is an operator applicable to the image is induced as shown in following Formula 4 by using Ls induced from Formula 3.
                              L          d                =                                                            L                s                            ⁡                              (                                  ⅈ                  ,                  j                  ,                                      t                    k                                                  )                                      *                          (                              1.0                +                                                                            L                      s                                        ⁡                                          (                                              ⅈ                        ,                        j                        ,                                                  t                          k                                                                    )                                                                                                  L                      white                      2                                        ⁡                                          (                                              t                                                  k                          -                          1                                                                    )                                                                                  )                                            1.0            +                                          L                s                            ⁡                              (                                  ⅈ                  ,                  j                  ,                                      t                    k                                                  )                                                                        FORMULA        ⁢                                  ⁢        4            
The operator Ld gained from Formula 4 is applied to a color image Cw input from following Formula 5 and a final output image Cd is gained. Here, Cd is referenced to as Rd, Gd and Bd.
                              C          d                =                              L            d                    *                                    (                                                C                  w                                                  L                  w                                            )                        γ                                              FORMULA        ⁢                                  ⁢        5            
In this way, the related WDR image generator performs a log operation with respect to the natural log and the exponential function. Because of that, the related WDR image generator has a relatively large load for performing real-time both of processing another image, the natural log operation, and the exponential function. In addition, WDR image generator is difficult to synchronize with the other blocks.
Furthermore, the related WDR image generator has to perform above Formula 3 to Formula 5 whenever each of the pixels is inputted in the blocks. Because of that, the related WDR image generator has to perform 4 division log operations that require the largest space and much time. As a result, the related WDR image generator is not appropriate for a high resolution image higher than 8 mega pixel level that requires a high speed clock.
Still further, the related WDR image generator uses the color space transfer calculation for performing the real-time image process as shown in Formula 1 and it would cause color distortion of the image because of correlation between the color component and the luminance component in the actual image. To prevent such color distortion, operators making proper computational adjustments may be required to correct color distortion, such as Formula 3 to Formula 5. In addition, flexibility of the image processing algorithm would deteriorate because the tuning point (γ) of Formula 5 is added.